Gas chromatography (GC) is a physical method for the separation, identification, and quantification of chemical compounds. A sample mixture is injected into a flowing neutral carrier stream and the combination flows through a tube or chromatographic column. The inner surface of the column is coated or packed with a stationary phase. As the sample mixture and carrier stream flow through the column, the components within the mixture are retained by the stationary phase to varying degrees depending on the relative volatility of the individual components and on their respective affinities for the stationary phase. Different chemical compounds are retained for different times by the stationary phase. When the individual mixture components are released into the carrier stream by the stationary phase, the components are swept towards the column outlet to be detected and measured by a detector. The specific compounds in the components of the mixture can be identified and their relative concentrations determined by measuring peak retention times and peak areas, respectively.
A current trend in chromatography is towards improving sample cycle time to increase customer throughput. Cycle time includes sample injection time, oven heating time, sample separation time, and oven cooling or equilibration time. To decrease sample residence time, ovens are increasingly becoming more powerful (higher wattage coils) and smaller (lower thermal mass). As the size of the oven shrinks, often the ductwork for the oven's intake and exhaust becomes more complex in order to fit in smaller places or to be located more remotely from the oven.
A geometry that is utilized in small and fast GC ovens includes one or more axial boxer intake fans connected to an intake duct of convergent geometry. The intake fans supply fresh air to the GC oven through the converging intake duct. The use of a converging intake duct allows larger intake fans located remotely from a small oven to be used during cool-down. However, further improvements can be made to this system to cool the oven more quickly.